1. Field of the Invention
The present invention relates to a compressor, and in particular to an apparatus and a method for controlling operation of a reciprocating compressor by estimating a stroke of the reciprocating compressor.
2. Description of the Prior Art
FIG. 1 is a block diagram illustrating a construction of an operation control apparatus of a reciprocating compressor in accordance with the conventional art.
As depicted in FIG. 1, the operation control apparatus of the reciprocating compressor includes a current detector 4 for detecting current applied to a motor (not shown) of a reciprocating compressor 6, a voltage detector 3 for detecting a voltage applied to the motor, a stroke calculator 5 for calculating a stroke estimation value of the compressor 6 on the basis of the detected current, voltage and parameters of the motor, a comparator 1 for comparing the calculated stroke estimation value with a preset stroke reference value and outputting a difference value according to the comparison result, and a stroke controller 2 for controlling a stroke of the compressor 6 by-varying a voltage applied to the motor according to the difference value. Hereinafter, the operation of the operation control apparatus of the reciprocating compressor will be described.
First, the current detector 4 detects current applied to the motor of the compressor 6 and outputs the detected current to the stroke calculator 5. Herein, the voltage detector 3 detects a voltage applied to the motor and outputs the detected voltage value to the stroke calculator 5.
The stroke calculator 5 calculates a stroke estimation value of the compressor with Equation 1 by substituting the detected current value, the detected voltage value and the parameters of the motor and applies the calculated stroke estimation value to the comparator 1.                     X        =                              1            α                    ⁢                      ∫                                          (                                                      V                    M                                    -                  Ri                  -                                      L                    ⁢                                          i                      _                                                                      )                            ⁢                              ⅆ                t                                                                        Equation  1            
Herein, R is resistance, L is inductance, α is a motor constant, VM is a voltage applied to the motor, i is current applied to the motor, and ī is a time variation rate of current applied to the motor. In more detail, ī is a differential value (di/dt) of i.
Afterward, the comparator 1 compares the stroke estimation value with the stroke reference value and applies a difference between the stroke estimation value and the stroke reference value according to the result of the comparison to the stroke controller 2.
The stroke controller 2 controls a stroke by varying the voltage applied to the motor of the compressor 6 on the basis of the above difference. It will be described in detail with reference to accompanying FIG. 2.
FIG. 2 is a flow chart illustrating an operation control method of the reciprocating compressor in accordance with the conventional art.
First, when a stroke estimation value is applied from the stroke calculator 5 to the comparator 1 as shown at step SP1, the comparator 1 compares the stroke estimation value with a stroke reference value and outputs the difference between the stroke estimation value and the stroke reference value according to the result of the comparison result to the stroke controller 2 as shown at step SP2.
When the stroke estimation value is less than the stroke reference value, the stroke controller 2 increases a voltage applied to the motor in order to control a stroke of the compressor 6 as shown at step SP3, and when the stroke estimation value is greater than the stroke reference value, the stroke controller 2 decreases a voltage applied to the motor as shown at step SP4.
As described above, in the apparatus and the method for controlling operation of the reciprocating compressor in accordance with the conventional art, a stroke estimation value is calculated by using parameters (motor constant, resistance, inductance) of the motor, and a stroke of the compressor is controlled on the basis of the calculated stroke estimation value. Accordingly, an error in the calculated stroke estimation value is increased due to variation in the parameters of the motor (in particular, resistance and inductance) and non-linearity.
In addition, in the apparatus and the method for controlling operation of the reciprocating compressor in accordance with the conventional art, because an error in the calculated stroke estimation value is great, it is impossible to control operation of the compressor accurately or precisely.